The value of tMirrorLiSourceNatSrcMacAddr specifies the Source MAC
Address field of the of the ethernet encapsulation used for the NAT
subscribers associated with this mirror source.
The value of tMirrorLiSourceNatSrcMacAddr is only useful
if the value of tMirrorDestinationEncapsulation of the corresponding
mirror destination is equal to 'ether'.
If no value for tMirrorLiSourceNatSrcMacAddr is specified, the value
of TIMETRA-CHASSIS-MIB::tmnxChassisBaseMacAddress is used.